1. Field of the Invention
The invention relates to a method for producing transparent conductive film glass, and more particularly to a method for producing transparent conductive film glass on a float glass production line.
2. Description of the Related Art
Having wide band gap, high transmittance of visible light, and high conductivity, transparent conductive film glass is widely used for preparation of display devices, thin film resistors, thin film switches, and solar cells. Although conventional tin-doped indium oxide (ITO) thin film has excellent photoelectric properties and mature commercial production process, the production cost is high and the thin film has poor corrosion resistance, which greatly limits its application. ZnO-doped thin film has low production cost and its properties can match those of ITO thin film, but it is difficult to form a uniform and stable film in a large area. If a conductive film is directly coated on the surface of hot glass, sodium ions inside the glass is likely to move to the surface of the glass and react with chloride ions inside the film to form sodium chloride. Thus, the film structure is destroyed, resulting in high surface resistance and surface turbidity.
As one of important application fields of transparent conductive film glass, solar cells not only require high transmittance of visible light and high conductivity, but also require high light absorption so as to increase short-circuit current. The haze can be enhanced by increasing surface roughness and texture of conductive film, which is beneficial to scatter light and increase optical path. Conventional methods for depositing includes vacuum magnetron sputtering, thermal evaporation, atomic layer epitaxy method, thermal spraying, pulsed laser deposition, sol-gel method, chemical vapor method, etc.
Chinese Patent ZL 88106876 discloses a method of depositing a layer of tin oxide on the glass in non-oxidizing atmosphere in a tin bath of float glass production line, i.e., with an oxidative gas (particularly air) as a carrier, a coating (particularly butyl tin trichloride) is deposited on the surface of glass to form a layer of metal oxide film. Since the temperature of the glass is high and uniform, the method has high reaction efficiency. However, the oxidative gas may oxidize the tin liquid, and after a certain time, the working conditions of tin bath will degenerate. Chinese Patent Application No. 96110665.4 discloses a method of depositing tin oxide on a moving plate glass or on a float glass substrate by chemical vapor deposition, the method comprising depositing a gas mixture consisting of anhydrous hydrogen chloride, tin tetrachloride, and water to the surface of the glass. Actually, the tin oxide film of both of the above-mentioned patents is just a single layer, and no barrier layer involved in, therefore, coherent iridescence will occur.
Chinese Patent ZL 01142650.0 discloses a method of depositing a barrier layer in a tin bath and a low emissivity layer in an annealing lehr respectively with float glass production line. The production method is stable and the resultant conductive film is uniform and has low emissivity. However, the surface resistance is higher than that required for preparing solar cells, the haze is low and no haze control agent involved in. Thus, the method cannot produce conductive film glass having low resistance and moderate haze.